Field
The present disclosure relates to an electrochemical device, and more particularly, to an electrochemical energy storage device.
Discussion of Related Art
Lithium secondary batteries produce electrical energy due to a redox reaction occurring when lithium ions are inserted/released from a positive electrode and a negative electrode. The positive electrode and the negative electrode includes active materials capable of inserting and releasing the lithium ions, and an electrolyte solution is loaded between the positive electrode and the negative electrode.
Recently, while a carbon-based negative electrode active material such as graphite is widely used, the upper limit of theoretic capacity is limited to approximately 372 mAh/g, and thus is insufficient as a negative electrode material corresponding to a mobile digital convergence device requiring high capacity. To compensate for this defect, there is an attempt to improve theoretical capacity using a silicon-based negative electrode active material.
However, the silicon-based negative electrode active material is changed in a crystalline structure when lithium is absorbed and stored, thereby having a great change in volume of 300% or more. As integrity of components is destroyed due to such a volume change, a capacity retention ratio is considerably decreased.